1. Field of the Invention
The present invention relates to internal time-triggered communication systems, and more particularly to a system configured to optimize the static segment schedule and cycle length of a time-triggered communication protocol having homogeneous slot sizes.
2. Discussion of Prior Art
Internal communication protocols have been developed to enable electronic inter-nodal communication and function in various applications. Conventional protocols and networking standards, such as Local Interconnect Networks (LIN), Media Oriented System Transport (MOST), and Controller Area Network (CAN) systems control electrical communication between the various nodes and a host controller.
In the vehicle manufacturing industry, protocols support the instrument panels, clusters and other electrical devices of vehicles, such as automobiles, aircrafts, recreational vehicles, and boats. For example, electromechanical power-assisted steering and anti-lock brakes may rely upon a communication network and protocol to receive electric signals from a controller that communicates with various speed and control sensors. As functionality and amenities, such as entertainment and computer systems, become increasingly inclusive, and driven by electromechanical and electro-software means, the necessary capacity, flexibility, and reliability of these protocols and network systems become increasingly critical for proper and safe operation. The introduction of advanced control systems that often combine multiple sensors, actuators and electronic control units also place boundary demands on conventional communication systems.
As a result, one type of communication system, the FlexRay™ communications protocol (“FlexRay”), has been developed for increasing the bandwidth, determinism, flexibility, scalability, and fault-tolerance of electronic communication systems. In contrast to conventional event-triggered automotive protocols, FlexRay, in this setting, combines time-triggered and event-triggered aspects to form a more robust system. More particularly, the FlexRay protocol presents a multi-channeled communications medium, wherein each channel includes static and dynamic segments during a communication cycle. A plurality of time-divisible-multiple-access (TDMA) slots of homogenous duration comprises the static segment and re-occurs each cycle. The TDMA slots are manually sized prior to automation, and each slot is randomly allocated to a node connected to the system, so that the node is able to constantly, and without collision, communicate with the network. The remaining bandwidth includes a dynamic segment divided into a plurality of mini-slots, wherein each mini-slot is configured to receive an event-triggered message, such as diagnosis data, of variable size.
The FlexRay protocol, however, presents a one-size-fits all application that limits performance. Once implemented, the slots-to-node assignments remain the same for each communication cycle. Of further concern, each signal from a node is randomly assigned to a slot in the set of slots assigned to the node, and each node operates autonomously, i.e. without scheduling or coordination, with respect to the other nodes. As such, static segment utility is reduced, where a more efficient schedule is available. Another concern is presented by the constant temporal dimension of the communication cycle length, where it is appreciated that excessively large cycle lengths waste bandwidth, and may thereby cause undue delays in the network, while cycle lengths consistently too small to handle the communication load result in excessive time-triggered backlog.
Thus, to further effect the intended benefits of the FlexRay protocol, there is a need in the art for an improved and flexible time-triggered communication system that can structurally adjust, so as to more efficiently transmit a given set of messages.